When using gtk-recordMyDesktop in Ubuntu some people face problems when recording together with audio. The problem that I faced was a bad recording and sometimes skipping seconds during the audio record. After searching around you may find some solutions, but each is responsible for the specific problem that it explains. In my case, I found another simpler solution without making modifications. When using gtk-recordMyDesktop you can disable audio recording, but record your audio with "Sound Recorder" that comes installed in Ubuntu. In the end of your recording session you will have 2 files, one containing the video and the other containing the audio. Now its time to mix them. By using "MKV files creator" (you can find it in the software repository) you can merge audio and video directly without losing quality. The operation is done in an instant, so you don't even need to wait.